Peocess of treating highly-porous paper-uke material



Patented June 11, 1929 UNITED STATES KIRKE L. .MOSES, F SPRINGFIELD,MASSACHUSETTS.

PROCESS OF TREATING HIGHLY-POROUS PAPER-LIKE MATERIAL.

No Drawing. Application filed May 28, 1923, Serial No. 642,084. RenewedAugust 4, 1928.

formed of loosely-matted fibres, and the further operation of subjectingsaid web or sheet to the action of a liquid for the purpose ofimpregnating it therewith. The sheet or web which is described in saidapplicationis one which has such a high degree of porosity and in whichthe fibres are so loosely matted together that it has very littleinherent strength,.in fact so little that when the paper is wet it isvery apt to break or tear apart by its own weight, especially if it isbeing acted uponby rollers or other similar devices While it is in a wetcondition.

One of the objects of my present invention is to provide an improvedmethod by which a tender paper-like web of the character above describedor of a similar char.- acter can be successfully handled while in a wetor saturated state and without danger of its breaking or tearing apart.The use of my invention thus enables me to take a tender paperlike websuch as above referred to and carry it through a bath containing waterby which the. web is thoroughlysat-- ui'ated without danger of itsbreaking or tearing apart during such treatment.

In my. above-mentioned patent a highlyporous loosely-matted web isdescribed as being subjected to a bath of latex or rubber emulsion forthe purpose of impregnating it therewith. Such rubber emulsion containsa certain percent of water and the action of the water on aweb ofsuflicient porosityv or absorbency to allow of its being impregnatedwith the rubber emulsion or latex reduces the strength of the web tosuch an extent thatit is very apt to break or tear apart as abovedescribed.

While the present invention is highly advanta eous in connection withthe process descri ed in the above-mentioned patent wherein this tenderweb is impregnated with rubber emulsion, yet the invention is equallyapplicable. in connection with any treatment of a tender web whichinvolves the wetting of the web because the application of my inventionto such method prevents the wet web from tearing or falling apart duringany treatment to which it may be subjected and which entails the use-0fwater.

While the present invention contemplates any suitable'way of preventingthis highlyporous tender paper-like web from tearing or falling apartwhen it has been wet during some treatment thereof, yet in general itmay be stated that the desired end may be accomplished by incorporatingin the paper some strength-giving element which gives the paper thenecessary strength when it is wet to prevent it from tearing apart butwhich. at the same time does not diminish appreciably the necessary highporosityof the paper, or render the paper appreciably less pervious toWater. Such strength-giving element may be incorporated in thepaper-like material either before it is formed into the web and while itis in the pulpy state or after it has been formed into the web or sheet.7

In practising the invention some strengthgiving element, such forinstance as rubber latex, is incorporated in the pulp either in thebeater or at some other stage in the paper-making operation before thepulp is formed into the web. The strength-giving constituent which isthus used may however be of any desiredcharacter so long as it willaccomplish the required purpose of giving strength to the tender Webwhen formed without diminishing appreciably its poros' ity or itscapability of becoming saturated with water and the inventioncontemplates the use of any material by which these re sults aresecured. It is important, however, that the strength-giving constituentshould be of such a nature that its presence in the paper stock .willnot detract appreciably from the porosity of the web when it is formedand if rubber latex is used as a strength-giving element it is desirableto; use it in relatively small proportions.

The strength-giving constituent may be also incorporated in the webafter it isv formed from the pulp, but, of course, before the webis-subjected to the impregnating op eration. This incorporation of thestrengthgiving element into the web may be accomplished in various waysas for instance by spraying onto the web a solution which contains latexor rubber or some other similar constituent that will impart the desiredstrength to the tender web without, however, detracting appreciably fromits porosity.

This spray of the rubber latex onto the web may be accomplished by meansof any usual spray devices and immediately after the web leaves thepaper-making machine or at any stage prior to the impregnation of theweb. .Where the strength-giving constituent is delivered to the Web bythe spray process it is desirable that the amount of rubber latex orother strength-giving material which is sprayed onto the web should berelatively small and only sufficient to give the web the added'strengthnecessary to enable it to be handled. readily during the impregnatingprocess, it being necessary and desirable that the porous character ofthe web should not be reduced or appreciably effected by theincorporation of the strength-giving element into the Web.

Still another way of incorporating the strength-giving element into thehighlyporous web before the impregnating process is to subject the webafter it is formed to a very weak hydrocarbon rubber solution by which avery slight amount of rubber will be incorporated into the web. This maybe done by passing the web directly.

after it is formed or at any stage between its formation and theimpregnating process through a bath of the hydrocarbonrubber solution.bath should be so constituted that only a small amount'ol rubber will beincorporated in the web, that is, just sufficient rubber to give to theweb, enough added strength to prevent it from tearing apart by its ownweight when it is wet.

It is important that in the operation of incorporating thestrength-giving element into the Web the high porosity of the lattershould not be reduced because the highlyporous character of the web isrequisite to carry out the subsequent impregnating process.

Other ways of preventing this very tender web from tearing apart orbreaking when it is being subjected to a bath containing water and meansby which it becomes wet may be employed without departing from theinvention and while I have referred to various ways of practising theinvention yet this has been done merely for illustrative purposesandWithout any intention of limiting the invention to any or all of saidways.

The present invention is specially intended to be used in connectionwith a process of making a paper-like product which involves first theproduction of the highly- It is desirable, however, that this poroustender web or sheet of loosely-matted fibres and the subsequent step ofimpregnating said web or sheet with a solution con taining water andrubber or any other filling material which it is desired to incorporatein the porous Web, and it contemplates such a treatment of the web .orpaper prior to its impregnation with the waterecontaining solution aswill give the web a sufficient support either externally ,or internallyto prevent it frombrea'king or tearing apart when it has become wet andsaturated with the water-containing solution. My inven tion, therefiore,contemplates means for counteracting the weakening eiiect on the web dueto the saturation of the latter with the waterin the water-containingsolution and While I have preferred aboveto various ways ofaccomplishing this end yet I do not wish to be limited to any 01 them asthe invention contemplates any appropriate means for preventing such ahighly-porous web from tearing apart when being subj ected to awater-containing solution for the purpose of impregnating it while atthe same time maintaining the highly-porous character of the web whichis essential for the impregnation thereof.

I claim:

1. The method of making a paper-like product which consists mproducing apaperlike web having sufiicient porosity to permit it to be freelysaturated with a filling material containing rubber and water but:having so little strength it will hardly hold :together when wet,distributing throughout the web a strength giving element which does notdetract enough from. the porosity of the web to prevent the freesaturation thereof with the filling material, and impregnating said webwith said filling material.

2. The method of producing a paper-like product which consists informing a paperlike web of sufficient porosity to freely absorb rubberlatex and also having incorporated therein .a strength-giving element,

which gives sufficient strength .to the web when the latter is wet toprevent it from tearing apart and then impregnating said web with rubberlatex.

3. The method of producing a paper-like product which consists informing a highlyporous paper-like Web of loosely-matted fibres,impregnating said web with a liquid filling material containing waterand before the Web is subjected to the impregnation process,incorporating therein a constituent which gives to thewe'b sufiicientstrength to prevent it from tearing apart when wet but which does notappreciably decrease the high porosity of the web or its capacity tobecome saturated with the filling material.

4. The method of producing a paper-like product which consists informing a highlyporous paper-like Web of loosely-matted fibres, WhichWeb has so little strength that it Will hardly hold together when Wet,incorporating in the paper stock a strengthgiving element which addssuflicient strength to the Web so that it will hold together when Wetbut which does not detract from the high porosity of the web and subsequently impregnating said Web with a filling material containin rubberand water. 10 In testimony whereo I have signed my name to thisspecification.

KIRKE L. MOSES.

